In this study, the first to evaluate laser treatment zones larger than 6.5 millimeters, 352 eyes of 186 patients underwent LASIK for correction of nearsightedness and nearsightedness with astigmatism. The treatment zones varied from six to eight millimeters, depending on the size of the patient's pupil, degree of astigmatism and amount of needed correction.
Among patients with nearsightedness, nearly 56 percent achieved uncorrected visual acuity of 20/20 or better; among those with nearsightedness with astigmatism, nearly 62 percent achieved 20/20 or better. In addition, preoperative best-corrected visual acuity and best spectacle-corrected contrast sensitivity were maintained.
Brian S. Boxer Wachler, MD, co-author of the study and a faculty member at the UCLA Medical Center, Jules Stein Eye Institute, said, "We know that corneal aberrations and night vision disturbances after LASIK are directly proportional to the degree of nearsightedness corrected and the size of the clearance zone – that is, the difference between pupil size and the optical zone treated by the laser. With this study, we now know use of large optical zones is safe and effective in preventing nighttime glare and haloes in patients with large pupils."
"This study shows using ablation zones from six to eight millimeters did not pose a problem in terms of safety. If anything, the larger optical zones had a higher percentage of eyes achieving 20/20 and 20/40 uncorrected visual acuity than the smaller zones," said Academy spokesperson James J. Salz, MD, clinical professor of ophthalmology at the University of Southern California and attending ophthalmic surgeon at Cedars-Sinai Medical Center in Los Angeles. "A subjective report on the patients' satisfaction with their night vision outcomes and measuring these treated eyes with wavefront studies to determine the level of postoperative higher order aberrations would be a good follow-up to this study."
Dr. Boxer Wachler estimates that 50 percent of patients who have the LASIK procedure done have large pupils and would benefit from large laser treatment zones because they would be less likely to have night vision disturbances.
The American Academy of Ophthalmology is the world's largest association of eye physicians and surgeons--Eye M.D.s--with more than 27,000 members worldwide. For more information about eye health care, visit the Academy's partner Web site, the Medem Network, at http://www.medem.com/eyemd. To find an Eye M.D. in your area, visit the Academy's Web site at http://www.aao.org.
Journal
Ophthalmology